N-succinimide additives for azide imaging systems

ABSTRACT

Dry photoimaging processes and compositions employing 1,8diazidonaphthalene and certain N-substituted succinimide additives in a permeable film-forming plastic are disclosed.

United States Patent Ando Dec. 18, 1973 [5 N-SUCCINIMIDE ADDITIVES FOR AZIDE 3,062,650 11/1962 Sagura et a1. 96/90 R IMAGING SYSTEMS 3,072,485 1/1963 Reynolds et a1. 96/91 N 3,092,494 6/1963 Sus e161. 96/91 N Inventor: HM Ando, Stamford. Conn. 3,282,693 11/1966 Sagura et a1. 96/91 N 3,287,128 11/1966 Lugasch 96/91 N [73] Assgnee' empany 3,519,425 7 1970 Marshall et al. 96/91 N Stamford Conn- 3,598,586 8/1971 Gaspar 96/75 [22 Filed; No 3 1972 3,617,278 11/1971 Holstead et al. 96/90 R [21] App]. No.: 303,575

Primary ExaminerJ. Travis Brown 62 I I Related Apphcatlon Data Assistant Examiner-Edward C. Kimlin Dlvlslon of Ser. No. 147,1 1 1, May 26, 1971, Pat. No. Atmmey R0bert Raymond [52] US. Cl 96/48 R, 96/9] N, 96/49, A

96/75, 96/90 R, 96/115 R 57 ABSTRACT [51] Int. Cl .L G036 5/24 [58] Field Of Searc 96/9l 90 9 PC, Dry photoimaging processes and compositions em- 115 115 48 R ploying 1,8-diazidonaphthalene and certain N- substituted succinimide additives in a permeable film- References Cit! forming plastic are disclosed.

UNITED STATES PATENTS 3,042,515 7/1962 Wainer 96/90 R 4 Claims, 1 Drawing Figure VISUAL D/FFUSE OPT/CAL DENSITY PATENTEDDECI 81975 0 N0 ADD/T/VE U h D 5% was /.s A 5% was I l I l I l l l STEP TABLET OPT/CAL DENSITY N-SUCCINIMIDE ADDITIVES FOR AZIDE IMAGING SYSTEMS The present application is a divisional of application Ser. No. 147,111, filed May 26, 1971, now US. Pat. No. 3,716,367.

This invention relates to photosensitive compositions and processes for the formation of images having broad spectra absorption characteristics and enhanced optical densities. More particularly, it relates to the use of various N-substituted succinimide additives in imaging systems employing 1,8-diazidonaphthalene.

Photosensitive compounds, compositions and processes play an essential role in photography and the related arts dealing with the formation of images with the aid of some activating influence, such as light, heat, etc. For many applications, as in the case of printing on white paper, it is desirable to maximize the neutrality and optical density of the image, in addition to achieving good color stability, speed, acuity, resolution and tonal range. It is also desirable to achieve these advantages by means of a convenient, dry imaging process employing relatively inexpensive materials.

Accordingly, it is an object of the present invention to provide photosensitive compositions which are suitable for the formation of images having broad spectral absorption characteristics of the imaged species, high optical densities, as well as goodimage stability, acuity, resolution and tonal range. It is a further object to provide a convenient, dry photoimaging process for the formation of such images. These and other objects and advantages of the present invention will become apparent from the description and examples which follow.

In accordance with the present invention, it has been unexpectedly found that the images produced by means of irradiating the photosensitive compound, 1,8- diazidonaphthalene, can be substantially improved by employing, in combination therewith, an N-substituted succinimide of the following structure:

wherein X is a member of the group consisting of --Br,

Cl and OH.

The additives of the present invention, namely, N- bromosuccinimide, N-chlorosuccinimide and N- hydroxysuccinimide are well known and can be obtained from a variety of commercial sources.

The photosensitive compositions of the present invention are prepared by uniformly distributing a photosensitive layer of polymer dope over the surface of a conventional photographic substrate. The polymer dope comprises a conventional, vapor permeable filmforming plastic having incorporated (preferably as a solution) therein the photosensitive compound, 1,8- diazidonaphthalene, and one or more of the above succinimide additives. One or more conventional light sensitizers may also be employed to extend the sensitivity of the composition into the range of from 360 mg to 470 mp or greater.

Suitable substrates include, for example, such materials as paper, plastic, wood, metal and glass.

Among the suitable conventional polymeric binders one may mention, for example, polyvinyl chloride. polyethylene, polymethylmethacrylate, polyvinyl acetate, cellulose acetate, copolymers of the corresponding monomers, and mixtures of the above polymers and the like. Polyvinyl chloride is especially preferred.

Suitable commercially available film forming polymers include, for example, the polyvinyl chloride polymers: Geon 101,101X13,105EP by the B. F. Goodrich Company and Dow PVC-166 by the Dow Chemical Company; polyvinyl chloride-polyvinyl acetate copolymers: Geon 421 by the B. F. Goodrich Company; chlorinated polypropylene, Parlon P-lO by the Hercules Powder Company, polyvinyl acetate copolymers, Gelva C-5, V16R by the Monsanto Company and the like.

The sensitized polymer dopes are prepared by form ing a uniform solution of the aromatic azide and the succinimide additive in the polymeric binder. This can be conveniently achieved through the use of an organic solvent, such as, tetrahydrofuran or toluene, into which the polymeric binder, azido photo-sensitive compound, succinimide additive and other desired ingredients are dissolved. The resulting solution can be applied to the photographic substrate by any conventional coating technique. The substrate is then prepared for imaging by removing the solvent from the dope by evaporation.

In general, any conventional coating techniques employed in large and small scale coating operations may be employed in preparation of the photosensitive systems. Of the suitable methods of applying the sensitized dope to the substrate, the Fixed Blade Method, the lmbibing Method and the Meyer Rod Method are among the preferred techniques.

In the Fixed Blade Method, the base material is positioned under a fixed blade and an excess of the coating material is placed on the base. The base is then passed under the blade to produce a uniform coating having a thickness determined by the distance between the mounted blade and the base material.

In the lmbibing Method, a substrate having a plastic surface is coated with the active compound by passing it under a roller, touching a solution of the azido compound. The excess coating is removed from the surface by an air knife. By way of illustration, one may mention passing paper coated with polyvinyl chloride, polyvinyl acetate or polymethylmethacrylate through a solution of 1,8-diazidonaphthalene and N-chlorosuccinimide in a solvent such as tetrahydrofuran, methyl ethyl ketone, acetone or toluene or mixtures thereof.

In the Meyer Rod Method, the coating composition is placed at one end of the base material and a metal rod wound with line wire is passed through the liquid causing it to be spread over the surface of the base material. The thickness of the coating produced by this method is determined by the size of the wire used in the winding.

The concentrations of azido compound and succinimide additive advantageously employed in the coating compositions and the thickness of the layer applied to the base may be varied to tailor the photosensitive system to achieve the desired degree of imaging speed, length of fixing period, image density, etc. Optimum concentrations and thicknesses will, of course, vary depending on the particular photosensitive compound and succinimide additive employed, the binder material and thickness of the binder layer used, fixing time and temperature, among other factors. In general, satisfactory photoimages can be produced using binder compositions having from about 1 percent to about 30 percent by weight of the azido compound and from about 0.1 to about percent by weight of the succinimide additive with coatings of from about 0.05 to about 1.00 mils in thickness. Preferred concentrations of the succinimide based on the l,8-diazidonaphthalene and thicknesses are from about to about 50 percent by weight and about 0.3 mils, respectively.

Generally, background colorup and diffusion time increase exponentially with film thickness. However, they are relatively unaffected by increases in the concentration of the azido compounds.

The l,8-diazidonaphthalene is sensitive to radiation containing wavelengths within the ultraviolet region. By means of the addition of a sensitizing agent to the polymer binder, the sensitivity can be extended into the range of from 360 m to 470 u or greater. The energy transfer of such systems is surprisingly efficient in view of the typically high viscosity of the binder polymer systems being sensitized.

Several advantages are provided by the use of sensitized systems. They permit the use of apparatus equipped with inexpensive and convenient light sources, such as incandescent lamps, and allow projection printing through various optical systems with normal optical glass. They also permit the simultaneous use of both direct and indirect excitation of azido compounds through simultaneous exposure of the photosensitive compounds to both visible and ultraviolet absorbing sensitizer in combination with the azido composition.

Suitable sensitizers include, for example, fluoranthene, thioxanthrone, fluorenone, perylene, benzanthrone, benzophenone, phenazine and thioacridone.

Sensitizers which absorb light in the visible spectrum are of necessity colored compounds. Where the colors caused thereby are found to be objectionable, one may employ a volatile, film-permeable sensitizer, such as fluorenone, or benzanthrone. In each case, the sensitizer will diffuse out of the binder composition during the fixing process.

Optimum relative concentrations of the sensitizer and azido compound will, of course, vary with the particular system being employed. Generally, energy transfer is favored by high concentrations of the azido compound. It is preferred to employ the sensitizer in a sufficient concentration to completely absorb the incident light. However, excessively high concentrations of the sensitizer will cause complete absorption of the incident light at the surface of the plastic matrix and may thereby reduce the efficiency of the system.

In the preparation of black and white images, it is generally desirable to maximize the optical density of the image produced. One means of achieving this result is to increase the concentration of the 1,8- diazidonaphthalene employed as the photosensitive compound. This approach, however is limited by the solubility of the l,8-diazidonaphthalene in the polymer binder selected. Where the solubility is exceeded, crystallization of the azide occurs in the photosensitive composition. Such a result is highly undesirable due to the fact that uniformity of composition is required for satisfactory image formation. In addition, the molecular nature of the imaging is destroyed and one obtains grain" as with conventional silver imaging processes.

It has unexpectedly been found that N- bromosuccinimide functions as a crystallization depressor, enabling the use of higher concentrations of the azido compound to achieve an enhanced optical density in the images produced. In addition, this additive also functions to promote the formation of more neutral images than those produced in the absence thereof.

It is generally preferred to employ N- bromosuccinimide in concentrations in the range of from about 1 to about 30 percent and 1,8- diazidonaphthalene in concentrations in the range of from about 0.1 to about 20 percent.

N-chlorosuccinimide also functions to broaden the spectral characteristics of the images produced with l,8-diazidonaphthalene. In addition, this additive unexpectedly permits the formation of images of enhanced contrast by substantially increasing the optical density of the exposed areas while producing only small increases in the optical density of the background, as seen, for example, in the attached figure. It is generally preferred to employ this additive in the concentration ranges indicated above for the bromo analog.

The N-hydroxysuccinimide additive functions to greatly enhance the optical density of the images produced with l,8-diazidonaphthalene and to broaden the spectral characteristics of the images produced therewith. In the practice of the present invention, it is generally preferred to employ this additive in the concentration ranges specified for the bromo analog above.

A convenient source of ultraviolet radiation is provided by lamps which emit a wide range of ultraviolet frequencies. A light table equipped with a film transparency (positive or negative) and a bank of ultraviolet-rich fluorescent lamps, such as, 15 Watt Black Light, No. Fl ST8-BL by General Electric and Rayonet Photochemical Reactor Lamps, No. RPR 3000A by The Southern New England Ultraviolet Company provides a convenient source of activating radiation. Conventional azo printing machines, equipped with high pressure mercury vapor lamps may also be employed. Since they emit both visible and ultraviolet light, they are especially well adapted for use with those compositions having sensitizers to visible light.

Absorption of incident light can be maximized by matching the frequencies of the incident light with the absorption frequencies of the aromatic azido compound or the sensitizer.

Patterning of the activating radiation can generally be achieved by any of the conventional methods. Suitable methods include passing the light through a film transparency or a template, use of a cathode ray tube containing an ultraviolet phosphor, such as, a Litton Industries Cathode Ray Tube, Serial No. 4188, which contains a P16 phosphor; and using an ultra-violet pen light, such as Ultraviolet Products, Inc. Pen-Light, or ultraviolet laser, such as might be used in spatial frequency modulation and holographic information storage, etc.

Optimum periods of irradiation will vary widely, depending upon the particular photosensitive composition, opacity of transparency, and light source employed. Exposure for a few seconds in a conventional diazo printer is generally adequate while periods of two minutes or more may be required for a source such as the abovementioned light table.

In the formation of images from 1,8- diazidonaphthalene in combination with one or more of the above N-substituted succinimide additives, it is generally preferred to fix the neutral image produced by heat. This is conveniently achieved by heating the exposed substrate to a temperature sufficient to volatil ize the unreacted azido compound from the polymeric binder. The optimum temperature and heating period will vary with the particular system employed and the heating means used. In the case of polyvinyl chloride binders, this can generally be achieved by heating the exposed composition at 135C. for a period of from about 1 to about 5 minutes or less.

Thermal fixing of the images can be achieved by merely placing the exposed film or paper into an oven. However, any other conventional means of heating the substrate may be suitably employed. For example, the fixing process may be automated by providing a means for passing the photosensitive substrate through an area in which exposure takes place into a fixing area where it is heated, for example, by passing it under heating lamps or over a heated platen. Passage of a hot stream of air over the film surface is also advantageously employed. In addition to heating the upper surface of the exposed film or paper, volatilization of the unreacted azido compound from the background is thereby facilitated, greatly reducing the fixing time required.

The processes and compositions of the present invention are further illustrated by the following examples which are not to be taken as limitative thereof. In each case, the parts and percentages specified therein are by weight unless otherwise indicated.

EXAMPLE 1 Crystallization Suppression The unique ability of N-bromosuccinimide to inhibit crystallization of 1,8-diazidonaphthalene in photosensitive compositions is demonstrated by the following tests in which various additives were incorporated with the azido compound into a polyvinyl chloride copolymer (Geon 421 by B. F. Goodrich Co.). In each case, 0.03 g. of the azide were combined with 0.012 to about 0.024 grams of the additive. The resultant mixture was added to about 0.07 grams of the polymer and the resulting mixture was dissolved in 0.72 grams of tetrahydrofuran. The solution was applied as a uniform coating to a 3 mil polyester film (Celanar by the Celanese Corp.). The coating was achieved by means of a Gardner Automatic Mechanical Applicator equipped with a Gardner Knife. Prior to use, the coated films were airdried at room temperature to permit the solvent evaporation.

The dried films were exposed to image light by means of a LogEtronics Inc. imaging device equipped with twelve black light/blue (F8T5/BLB), G. E. fluorescent lights with a total black light intensity of about 4 mw/cm at the film plane. After imaging, the exposed films were briefly heated in an air circulated oven regulated to 135C. The crystallization data and color of the image produced for each additive are set forth in Table I below. Use of the succinimide additives of the present invention in each case resulted in substantial enhancement of the image neutrality; however, of the compounds tested, only N-bromosuccinimide resulted in a suppression of the tendency of 1,8-diazidonaphthalene to crystallize out of solution when employed in high concentrations.

TABLE I Crystallization Additive Tested Image Color of DAN None P" C N-Bromosuccinimide BB UC" N-Chlorosuccinimide BB 1111-v-u-w-u-u-u-v-e-e-q'e-v-v'w-w'u-u-u OOOOOOOQOOOOOOOOOOGOOQO EXAMPLE 2 In order to quantitatively evaluate the relative contrast achieved in 1,8-diazidonaphthalene imaging systems having image color modification by addition of N-chlorosuccinimide or N-bromosuccinimide, the following tests were performed.

Three photosensitive compositions were prepared using 3 mil films of polyester for support (Celanar by the Celanese Corporation of America). A control sample was prepared by coating the support film with a .4 mil layer of a polyvinyl chloride-polyvinyl acetate co polymer (Geon 421, by the B. F. Goodrich Company) containing 15% by weight of the photosensitive compound, 1,8-diazidonaphthalene. The coating composition was prepared by dissolving the polymer and photosensitive compound in tetrahydrofuran. The resulting solution was applied to the film substrate using the Gardner Knife coating technique. Prior to use, the solvent was permitted to evaporate from the binder composition.

Two test photosensitive compositions were prepared as in the case of the control composition above with the exception that the coatings were made 5% in N- bromosuccinimide and 5% in N-chlorosuccinimide, respectively.

The three test compositions were imaged by exposure to a LogEtronics Inc. imaging device equipped with twelve black light/blue fluorescent bulbs (F8T5/BLB by the General Electric Company) through a No. 1A Eastman Kodak, 10-step Densitometric Tablet for about 5 minutes.

The imaged systems were fixed by heating in a circulating air oven controlled at C. for a period of about 10 minutes. The developed and fixed image densities were measured by means of a Macbeth TD-l02 Densitometer Tablet. The relative contrasts of the images produced were determined quantitatively by preparing DlogE curves and determining gamma, 7, de-

fined as the maximum slope of the DlogE curves as projected on the logE axis. The data obtained for each system is graphically depicted in the attached figure. The image colors produced and the gammas observed are set forth in Table 11 below.

TABLE [I Additive Image Color 7 No AdditivcO Purple Purple-Black l.4l NCSD Deep Blue Gray-Black L72 5% NBS A Deep Blue Gray-Black L32 It is apparent from the results obtained, that the images prepared from the imaging systems employing N- bromosuccinimide and N-chlorosuccinimide are of substantially greater neutrality than those achieved in their absence. It is further evident that the N chlorosuccinimide system unexpectedly provides additional advantages by way of contrast. This additive permits the achievement of substantially enhanced optical densities without substantial impairment of the background optical densities; a combination of spectral and Densitometric characteristics which permit the preparation of photographs having a wide range of variation in tone with a completely neutral image in addition to the preparation of high quality, sharp lined images, without substantially darkening the image background. While such properties are especially useful in the preparation of black and white photographs on paper, they are also of great importance in preparing microfilms for the projection of high contrast straight line and continuous tone images.

EXAMPLE 3 The effect of N-hydroxysuccinimide on the images produced in 1,8-diazidonaphthalene photosensitive systems is demonstrated in the following tests.

The photosensitive compositions were prepared by the general procedure of Example 2 using a film coating prepared by dissolving 0.1 gram of N- hydroxysuccinimide, 0.17 gram of 1,8- diazidonaphthalene and 0.98 gram of polyvinyl chloride copolymer (Geon 421 by the B. F. Goodrich Company) in 8.85 grams of methyl ethyl ketone. Coatings 0.3 mil in thickness were prepared on 3 mil films of polyester (Celanar). The coated films were imaged by exposure in the previously mentioned LogEtronics Inc. U.V. light unit for 3 minutes and heat fixed for 2 minutes at 135C. A photopic density of 0.74 was observed in a control sample prepared as above without the addition of N-hydroxysuccinimide; while, photopic densities of 1.26 were achieved in the test samples employing N-hydroxysuccinimide.

EXAMPLE 4 The comparative photopic density of images prepared with photosensitive compositions containing 30% concentrations of l,8-diazidonaphthalene with N- chlorosuccinimide and N-bromosuccinimide additives is demonstrated by the following tests.

Photosensitive compositions were prepared by the general procedure of Example 3 above, using 0.36 gram of 1,8-diazidonaphthalene, 0.85 gram of filmforming polymer (Geon 421), 7.65 grams of methyl ethyl ketone, 1.13 grams of tetrahydrofuran and 0.l2 gram of the N-substituted succinimide to be tested. The compositions produced were in each case imaged by the procedure of Example 3 fixed by heating at C. for 3 minutes. The resulting image color and comparative photopic densities of the images produced are set forth in Table lll below.

TABLE lll Additive Image Color O.D. No Additive Purple 0.46 NCS Blue-Black 0.97 NBS Blue-Black 0.87

It can be seen that in each case a substantial enhancement in optical density (O.D.) was achieved through the use of the N-substituted succinimide additive in addition to a substantial enhancement in image color neutrality.

I claim:

1. A dry imaging process comprising the step of imaging a photosensitive element characterized as a photographic substrate having a coating deposited thereon, said coating comprising a vapor permeable filmforming plastic having l,8-diazidonaphthalene and a compound of the following formula uniformly dissolved therein:

i OT TO wherein X is a member of the group consisting of Br, Cl and -OH, by irradiation with image activating radiation.

2. A process according to claim 1 wherein said radiation is ultraviolet light.

3. A process according to claim 2 wherein the plastic is selected from the group consisting of polyvinyl chloride, polyvinyl acetate and vinyl chloride-vinyl acetate copolymers and the coating contains a concentration of 1,8-diazidonaphthalene in the range of from about 1 percent to about 30 percent by weight and contains a concentration of the succinimide in the range of from about 0.1 to about 20 percent by weight and said coating has a thickness of about 0.05 to about 1.00 mils.

4. A process according to claim 1 further comprising the step of heating the imaged composition to ,a temperature sufficient to effect removal of the unreacted 1,8-diazidonaphthalene from the film-forming plastic. t 

2. A process according to claim 1 wherein said radiation is ultraviolet light.
 3. A process according to claim 2 wherein the plastic is selected from the group consisting of polyvinyl chloride, polyvinyl acetate and vinyl chloride-vinyl acetate copolymers and the coating contains a concentration of 1,8-diazidonaphthalene in the range of from about 1 percent to about 30 percent by weight and contains a concentration of the succinimide in the range of from about 0.1 to about 20 percent by weight and said coating has a thickness of about 0.05 to about 1.00 mils.
 4. A process according to claim 1 further comprising the step of heating the imaged composition to a temperature sufficient to effect removal of the unreacted 1,8-diazidonaphthalene from the film-forming plastic. 